Electrodeposition of FeCrNi and FeCr alloys and influence of heat treatment on microstructure and composition

Abstract

The electroplating of iron-chromium and iron-nickel-chromium layers is an economic alternative to mild steel and hard-chrome layers from chromium (VI) electrolytes. Iron-chromium and iron-nickel-chromium layers were electrodeposited using an environment friendly chromium (III) electrolyte. The layers were heat-treated at different temperatures (150 °C, 300 °C, 450 °C and 600 °C) in order to determine the temperature at which recrystallization takes place, which phases are formed and to study the influence on the element content. The phase analysis was conducted by X-ray diffraction, the chemical composition and the microstructure were characterized by the scanning electron microscopy. Both layer systems show an X-ray-amorphous structure that begins to recrystallize at a temperature of 450 °C. From a heat-treatment temperature of 600 °C, the organic additives decompose and the oxygen forms chromium oxide with the chromium.

Electrodeposition of Thick and Crack-Free Fe-Cr-Ni Coatings from a Cr (III) Electrolyte

“…It is observed that the oxygen content is evenly distributed over the entire layer thickness in all layers. The oxygen values and curves of the DC and stepped DC samples correspond roughly to the results from a study on the heat treatment of Fe-Cr-Ni and Fe-Cr layers [11]. The use of PC reduces the incorporation of oxygen by approx.…”

“…The difference in electrochemical behavior between the electrodeposited Fe-Cr-Ni samples and the AISI 304 stainless steel is attributed to the dissimilarities in the microstructure and chemical composition of the passive oxide film [26]. As previously shown in the study on the influence of heat treatment on the microstructure of Fe-Cr-Ni coatings, electrodeposited Fe-Cr-Ni alloys are amorphous or nanocrystalline in contrast to its metallurgical crystalline counterpart [11]. In addition, the incorporation of oxides, chlorides, hydroxides, and hydrides by electrolyte additives into the coating leads to enhanced hydrogen evolution reactions [19,27] and a passive oxide layer that differs in chemical composition from that of AISI stainless steels.…”

“…Even fewer studies have dealt with the corrosion behavior of electroplated Fe-Cr-Ni coatings [9,10]. Pure chromium and electroplated Fe-Cr-Ni deposits are nanocrystalline, which lead to high residual stresses and thus microcracks in the coatings [5,11]. A characteristic of almost all chromium coatings is the formation of microcracks, which are associated with the discontinuous evolution of hydrogen [12].…”

Influence of the Current Regime during Electrodeposition in a Cr(III)-Containing Fe-Cr-Ni Electrolyte on the Near-Surface pH, Alloy Composition, and Microcrack Behavior

“…Furthermore, this co-deposition causes grain refinement. The result are nanocrystalline layers with a crystallite size of less than 2 nm [8,9]. In such a nanocrystalline structure, the inverse Hall-Petch effect occurs, which is documented in the literature for crystallite sizes smaller than 20 µm [10].…”